The present study is designed to provide information concerning the genetic control of aflatoxin production in Aspergillus flavus. This is to be accomplished by: (1) the induction of morphological and auxotrophic mutants, (2) the induction of aflatoxin variants, (3) the parasexual analysis of mutants to determine linkage of genes controlling aflatoxin production to known genetic markers, (4) the analysis of aflatoxins in haploids, diploids, and haploid segregants derived from diploids, and (5) the analysis of possible polygenic effects. Seven linkage groups have now been identified in A. flavus by means of the parasexual cycle. Twenty auxotrophic and morphological mutants have been assigned to these linkage groups. Several mutants producing different levels of aflatoxins B1 and B2 have been recovered and some have been examined in heterozygous diploids. Haploid segregants from these diploids indicate that more than one type of gene action may be involved. Segregants from certain diploids apparently differ by only a single gene whereas segregants from other diploids differ by the additive effect of several genes. BIBLIOGRAPHIC REFERENCE: Papa, K.E. 1976. Linkage groups in Aspergillus flavus. Mycologia. Jan.-Feb. issue.